But that's not all, I was then faced with a second problem - which turned out to be unsupported "stuff" left over in the /etc/X11/xorg.conf, in particular an "RgbPath" related config line - so this needed to be removed.

Update: Since these problems with 107, 108 has come out and it seems to address these issues, upgrading from 107 to 108 was completely painless and problem free!

Additional note:

Recently trying to install OpenSolaris 109 under VirtualBox 2.1.4 resulted in a frozen white screen before the graphical login. After some digging around and debugging the problem appeared to be an incompatibility with VirtualBox guest additions (GA).